..In conclusion, alterations in the amino acid sequence of the C terminus do not alter the mu-specificity of the receptor but they can influence the binding characteristics, efficacy, and potency of mu-opioids...

Identification and characterization of two new human mu opioid receptor splice variants, hMOR-1O and hMOR-1X

..Selective kappa(1) and delta opioids did not lower binding. Despite the dramatic increase in affinity for the opioid agonists in co-expressing cells, the opioid antagonists naloxone and diprenorphine failed to compete [3H]OFQ/N binding...

Stabilization of the μ-opioid receptor by truncated single transmembrane splice variants through a chaperone-like action

..These chemical biologic approaches were then eclipsed by the molecular biology revolution, which now reveals a complexity of the morphine-like agents and their receptors that had not been previously appreciated. ..

..It now appears that this gene undergoes extensive splicing, in which a single gene can generate multiple proteins. Evidence now suggests that these splice variants may help explain the clinical variability in responses among patients...